1. Field of the Invention
The present invention relates to a bar code reader for reading a bar code by applying a laser beam emitted from a laser diode to the bar code, and receiving reflected light therefrom through a photodetector.
2. Description of the Related Art
A bar code reader for reading a bar code by the agency of reflected light of light applied from a light source towards the bar code is in widespread use today in the distribution sector, sales control division, and so forth because of its capability of reading the bar code even if the bar code reader is at a good distance away from the bar code.
Among such bar code readers, there is available one equipped with a portable laser scanning head which a user can hold in one hand. When reading a bar code printed on goods, and so forth, by use of the portable laser scanning head, a laser beam is caused to be emitted therefrom to be directed towards the bar code as a target of reading so as to reciprocatively scan the bar code in such a way as to cut across it, whereupon the laser beam reflected from the bar code is detected, and the bar code is read by decoding the detection signals (refer to, for example, JP, 5-233862, A, JP, 6-187481, A, and so forth).
Thus, with a bar code reader equipped with a laser diode, laser light emitted from the laser diode of the laser scanning head is rendered into a thin beam form. Such a laser beam is deflected by rotation of a rotary optical deflector such as a polygon mirror, galvanomirror, and so forth, thereby scanning a part (bar code surface) on which a bar code is printed.
However, because the laser light emitted by the laser diode is at a wavelength, close to that of an infrared ray, and in a boundary region between the visible region and the invisible region, it is difficult to visually recognize the laser beam in an environment of bright ambient light. In addition, because a scanning speed is very fast, there has arisen a problem that it is impossible to visually recognize a scanning position and a width of the laser beam on the bar code surface, and it is difficult to sight a scanning head on a bar code, rendering it difficult to read the bar code accurately and efficiently.
To overcome such a problem as described, there has been disclosed in, for example, JP, 5-233862, A, an optical scanning device equipped with an optical sighting mechanism for sighting a handy type laser scanning head on a bar code to be read by the same.
The optical sighting mechanism, however, requires a pair of light sources for sighting, an optical system associated therewith, and so forth, thereby rendering the constitution thereof complex, and increasing the number of components thereof, so that not only a high cost results, but also an application method thereof is far from simplicity.
Further, with a bar code reader disclosed in, for example, JP, 2000-90189, A, a proposal has been made to install a pair of mirrors for deflecting a laser beam scanning the vicinity of the opposite edges of a scanning range by the laser beam deflected by a scanning mirror which rotatively reciprocates, towards the center side of the scanning range. It is intended to thereby increase a quantity of light irradiated to a predetermined part in the vicinity of the center of the scanning range, so that visibility of a scanning line by the laser beam is enhanced.
With this method, however, there is a need of disposing the pair of the mirrors as added at a position closer to the bar code surface than the scanning mirror, thereby creating a problem in that the scanning head becomes larger. Furthermore, because the scanning line by the laser beam needs to be recognized in a state where scanning by the laser beam is executed by rotative reciprocation of the scanning mirror, it has still been difficult to visually recognize the scanning line if a scanning speed is fast.